᪥ᮏࡢ࢔࣑࣓࢜࢘࢞
Green turtle of Japan

Ⓨห࡟࠶ࡓࡗ࡚ ࢔࣑࣓࢜࢘࢞ࡣⲡ㣗ᛶࡢ࣑࣓࡛࢘࢞࠶ࡿࠋࡘࡲࡾࠊ୍ḟᾘ㈝⪅࡞ࡢ࡛࠶ࡿࠋ⏕ែᏛⓗ࡟⪃࠼ࡿ࡜ࠊ୍ḟᾘ㈝⪅ࡣ஧ḟᾘ㈝⪅ࡼࡾᩘࡣከࡃࠊࡲࡓࠊࡼࡾ㧗ḟࡢᾘ㈝⪅ࢆᨭ࠼ࡿື≀࡛࠶ࡿࡇ࡜ࢆᡃࠎࡣㄆ㆑ࡍࡿᚲせࡀ࠶ࡿࠋୡ⏺ⓗ࡟࢔࣑࣓࢜࢘࢞ࡣ 19 ୡ⣖࠿ࡽ 20 ୡ⣖࡟኱ࡁࡃᩘࢆῶࡽࡋࡓ࡜⪃࠼ࡽࢀࡿࠋ⌮⏤ࡣ⨾࿡ࡋ࠿ࡗࡓ࠿ࡽ࡛࠶ࡿࠋࡋ࠿ࡶࠊ㝣࡟࠶ࡆ࡚ࡶ⏕ࡁ࡚࠸ࡿࡢ࡛ࠊಖᏑࡀࡁࡃ㣗ᩱࡔࡗࡓࠋᕹ⯪࡛ୡ⏺ࢆ⯟ᾏࡋ࡚࠸ࡓ᫬௦ࡶࠊὋࡄ࣑࣓࢘࢞ࡸ⏘༸ࡍࡿ࣑࣓࢘࢞ࢆᤕࡲ࠼࡚ࠊ⯪࡟ࡘࡳࠊᚲせ࡞᫬࡟㣗࡭ࡓࡇ࡜ࡶᐜ᫆࡟᝿ീ࡛ࡁࡿࠋ࣑࣓࢘࢞
ࢫ࣮ࣉࡶࡑࡢ㡭࠿ࡽዲࡲࢀࡿࡼ࠺࡟࡞ࡗࡓࡢࡔࢁ࠺ࠋࡓࡔࠊ⏘ᴗ㠉࿨ࡸ㈌ᖯ⤒῭ࡀୡ⏺ࡢ㝮ࠎࡲ࡛ᾐ㏱ࡍࡿࡲ࡛ࡣࠊࡑࢇ࡞࡟ࣂࣛࣥࢫࡀᔂࢀࡿࡇ࡜ࡣ࡞࠿ࡗࡓࠋ⇕ᖏࡢᾏᓊἢ࠸࡟⏕άࡢᣐⅬࢆᵓ࠼ࡓேࡓࡕࡣࠊࡓࡲ࡟⋓ࢀࡿ࢔࣑࣓࢜࢘࢞ࢆ㣗࡭ࠊ༸ࢆศࡅ࡚㣗࡭ࡓࠋࡑࡢࡼ
࠺࡞⩦័ࡣࠊ᪥ᮏ࡛ࡶ༡すㅖᓥ࡞࡝࡛᭱㏆ࡲ࡛ぢࡽࢀ࡚࠸ࡓࠋ࡜ࡇࢁࡀືຊ⯪ࡢฟ⌧ࡣࠊ㏨ࡆࡿ࢔࣑࣓࢜࢘࢞ࢆ㏣࠸࠿ࡅࠊࡑࢀࡀ᥮㔠ࡉࢀࡿࡇ࡜ࡀࢃ࠿ࡿ࡜⋓ࢀࡿ㝈ࡾ⋓ࡿࡼ࠺࡟࡞ࡿࠋ
ࡑࡋ࡚ୡ⏺ࡢ࢔࣑࣓࢜࢘࢞ࡣῶᑡࡋ࡚࠸ࡗࡓࠋ ᭱㏆ࠊ࢔࣑࣓࢜࢘࢞ࡣቑ࠼ࡓ࡜࠸࠺ࢹ࣮ࢱࡀୡ⏺ྛᆅ࠿ࡽሗ࿌ࡉࢀ࡚࠸ࡿࠋಖㆤᛮ᝿ࡀ
ᬑཬࡋࡓ࠿ࡽࡔࢁ࠺ࠋ࡜ࡇࢁࡀࠊಖㆤᛮ᝿ࡣ࣑࣓࢘࢞ࡢ࠸࡞࠸ඛ㐍ᅜ࠿ࡽጞࡲࡿࠋඛ㐍ᅜࡣ࣑࣓࢘࢞ࡢ࠸ࡿᾏ㎶࡟ࡍࡴேࡓࡕ࡟ࠊ࣓࢝ࢆ⋓ࡿ࡞ࠊ༸ࢆ⋓ࡿ࡞ࠊ࡜㏕ࡿࠋ☜࠿࡟ࡑࢀࡀຌࢆዌࡋ࡚࢔࣑࣓࢜࢘࢞ࡣቑ࠼࡚࠸ࡿࠋ༡すㅖᓥࡶ౛እ࡛࡞࠸ࠋ1980 ᖺ㡭ࡼࡾᾏ࡟ධࡗ
࡚࠸ࡿࡀࠊぢ࠿ࡅࡿ࢔࣑࣓࢜࢘࢞ࡢᩘࡣ᭱㏆᱁ẁ࡟ቑ࠼ࡓࡼ࠺࡞༳㇟ࡀ࠶ࡿࠋ୍ḟᾘ㈝⪅ࡣࢩ࢝ࡢ౛ࢆࡳ࡚ࡶゎࡿࡼ࠺࡟ࠊࡍࡄቑ࠼ࡿࠋቑ࠼ࡿ࡜᳜≀ࢆ㣗࡭ࡍࡂ࡚ࠊ⏕ែ⣔࡟῝้࡞ᙳ㡪ࢆཬࡰࡍࠋከศࠊ࢔࣑࣓࢜࢘࢞ࡶࡑࢀ࡜㢮ࡍࡿࡇ࡜ࡀ㉳ࡇࡿࡢ࡛࠶ࢁ࠺ࠋࡲࡔࠊ㆟ㄽ࡟ࡣ⮳ࡗ࡚࠸࡞࠸ࡀࠊ࢔࣑࣓࢜࢘࢞࡟ࡼࡗ࡚☾↝ࡅࡀ࠾ࡁࡓࡾࠊỈ⏘≀ࡢỈᥭࡆ࡟ᙳ㡪ࡀ࡛ࡓࡾࡍࡿࡇ࡜ࡶ࠶ࡿࡔࢁ࠺ࠋ ࡑࡢࡼ࠺࡞኱ࡁ࡞ኚ໬ࡢ୰࡛ࠊᡃࠎࡣ୕஭≀⏘⎔ቃᇶ㔠ࡢຓᡂࢆཷࡅ࡚ࠊ࢔࣑࣓࢜࢘࢞
ࡢ࣍ࢵࢺࢫ࣏ࢵࢺࢆ᥈ࡋฟࡋࡓࠋ࢔࣑࣓࢜࢘࢞ࡀἑᒣ㞟ࡲࡿᾏᇦ࡛࠶ࡿࠋ༡すㅖᓥࢆ୰ᚰ
࡟Ⅼᅾࡍࡿࡇࢀࡽࢆ௒ᚋࢢ࣮ࣜࣥࢱ࣮ࢺࣝࢧࣥࢡࢳࣗ࢔ࣜ࡜ࡋ࡚ࠊேⅭⓗ࡞ᨵኚࢆຍ࠼࡞
࠸ࡼ࠺࡟ࡋ࡚ࠊぢᏲࡗ࡚࠸ࡁࡓ࠸࡜⪃࠼࡚࠸ࡿࠋ࢔࣑࣓࢜࢘࢞ࡣ୍ḟᾘ㈝⪅࡛࠶ࡿࠋࡑࢀ
ࢆᏲࡿ࡟ࡣࠊᡃࠎࣄࢺࡀ೺඲࡞஧ḟᾘ㈝⪅࡟࡞ࡿࡇ࡜࠿ࡶࡋࢀ࡞࠸ࠋ

NPO ἲே᪥ᮏ࣑࣓࢘࢞༠㆟఍ ఍㛗டᓮ┤ᶞ



Prologue
The green turtles are herbivorous sea turtle, which is the primary consumer. The
existence of primary consumer, which number is larger than the secondary consumer, iscrucial for the flourish of high-order consumer and is, therefore, ecologically important.
The global population of green turtle dramatically decreased from the 19th to 20h
century due to consumption. Green turtles were also used as food source during thegreat expedition era since they survive on decks for a long time after being captured. It
is easy to imagine swimming or nesting sea turtles being caught as food source.
The human consumption and the green turtle population were well balanced until theindustrial revolution and monetized economy spread through the world. People shared
the green turtle meat and eggs amongst themselves. These traditions were also seen in
Nansei islands of Japan. However, the emergence of power-driven vessel chased andfished green turtles for money. The global numbers of green turtles decreased.
Recently, green turtles are increasing world-wide due to prosecution of conservation
projects. However, those projects are created in developed countries, which are mostly
ecologically and economically irrelevant to sea turtles. Project teams warn people not to
consume, hunt, and dig-up eggs: Nansei islands were not an exception. Those actions
are actually bringing back the sea turtle population: however, excessive increase inanimal number may lead to serious environmental problems such as decrease in
seagrass beds and decline in fish catch.
The NPO association, Japanese Sea Turtle Association received a fund from Mitsui
Co. to search for green turtle “hot-spots”. We are planning to select the Nansei-islands
as the green turtle sanctuary and protect them from human hands. Green turtles are theprimary consumer. Maybe us humans, need to act as good secondary consumers.

Director of Sea Turtle Association of Japan
Naoki Kamezaki┠ ḟ➨୍❶࢔࣑࣓࢜࢘࢞࡜ࡣ࡝ࡢࡼ࠺࡞ື≀࠿ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 1➨஧❶᪥ᮏ࡟࠾ࡅࡿ࢔࣑࣓࢜࢘࢞ࡢ⏕ែ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 23➨୕❶ୡ⏺ࡢ࢔࣑࣓࢜࢘࢞ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 43➨ᅄ❶ྛᆅࡢ࢔࣑࣓࢜࢘࢞ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 67➨஬❶࢔࣑࣓࢜࢘࢞ࡢಖ඲ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 99෗┿ᥦ౪⪅࣭ㅰ㎡ ࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭࣭ 122

Contents
Chapter One: An Overview of the Green Turtleᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 1

Chapter Two: Biology of the green turtles in Japanᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 23

Chapter Three: Green turtles of the Worldᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 43

Chapter Four: Green turtle from Various Areas of Japanᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 67

Chapter Five: Conservation of green turtlesᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 99

PhotographyὉAcknowledgmentᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ ᴾ 122

1

2

➨1❶ ࢔࣑࣓࢜࢘࢞࡜ࡣ࡝ࡢࡼ࠺࡞ື≀࠿ட⏣ ࿴ᡂ‫࡟ࡵࡌࡣە‬Ἀ⦖࡛ࢲ࢖ࣅࣥࢢࡢ⤒㦂ࡀ࠶ࡿேࡣࠊ୍ᗘࡣ࢔࣑࣓࢜࢘࢞ࢆぢࡓࡇ࡜ࡀ࠶ࡿࡢ࡛ࡣ࡞࠸
ࡔࢁ࠺࠿ࠋ㫽ࡀ⩚ࡤࡓࡃࡼ࠺࡟ඃ㞞࡟Ὃࡄጼ࡟ឤືࡋࡓேࡶ࠸ࡿ࡜ᛮ࠺ࠋ࢔࣑࣓࢜࢘࢞ࡣ
࣑࣓࢘࢞㢮ࡢ୰࡛ࡶ⨾ࡋ࠸ጼࢆࡋ࡚࠸ࡿ࡜ゝࢃࢀ࡚࠸ࡿࠋᑠࡉ࡞㢌࡟኱ࡁ࡞┠ࡀ࠶ࡾࠊ⏥ࡽࡣ⥡㯇࡞ὶ⥺ᙧࢆࡋ࡚࠸ࡿࠋ࣑࣓࢘࢞ࡣỈ᪘㤋ࡢேẼ⪅࡛࠶ࡿࡀࠊ୰࡛ࡶ࢔࣑࣓࢜࢘࢞
ࡢᏊ࣓࢞ࡀࡶࡗ࡜ࡶྍឡࡽࡋࡃேẼࡀ㧗࠸ࠋ࢔࣑࣓࢜࢘࢞ࡣୡ⏺࡟ 7 ✀㢮࠸ࡿ࣑࣓࢘࢞㢮ࡢ 1 ✀࡛࠶ࡿࠋ᪥ᮏ࡛ࡣ࢔࣑࣓࢜࢘࢞ࡢ௚
࡟ࠊ࠶ࡉࡦࡀࡵࠊṇぬᆓ㸦ࡋࡻ࠺ࡀࡃࡰ࠺㸧ࠊࡳࡌࡀ࣮ࡳ࣮࡞࡝ࡢูྡࡀ࠶ࡿࠋୡ⏺୰ࡢᬮ࠿࠸ᾏ࡟ఫࢇ࡛࠸ࡿࠋ࣑࣓࢘࢞㢮ࡢ୰࡛ࡶ᭱ࡶἢᓊᛶࠊࡘࡲࡾᓊࡢ㏆ࡃ࡟ఫࢇ࡛࠸ࡿࡓࡵࠊ
ฟ఍࠺ᶵ఍ࡶከ࠸ࠋࡑࢀ࡟ࣁ࣡࢖࡞࡝࡛ࡣࠊ◁὾࡟ୖ㝣ࡋ࡚ࣂࢫ࢟ࣥࢢ࡜ゝࢃࢀࡿ⏥ࡽᖸࡋࢆࡋ࡚࠸ࡿࠋࡇࡢࡓࡵほගᐈࡢࡍࡄᶓ࡛࣑࣓࢘࢞ࡀఇࢇ࡛࠸ࡿࡇ࡜ࡶ࠶ࡿࠋ㒔఍࡟ఫࡴே࡟࡜ࡗ࡚ࡣࠊ࢔࣑࣓࢜࢘࢞ࡣỈ᪘㤋ࡢ୰࡛ࡋ࠿ぢࡓࡇ࡜ࡀ࡞࠸ື≀࠿ࡶࡋࢀ࡞࠸ࠋࡋ࠿
ࡋࠊ᪥ᮏ࡛ࡶᆅᇦ࡟ࡼࡗ࡚ࡣ࡜࡚ࡶ㌟㏆࡞Ꮡᅾ࡛࠶ࡿࠋ዆⨾ࡸἈ⦖࡛ࡣᓊ࠿ࡽ࡛ࡶほᐹ࡛ࡁࡿࡋࠊ ࡢ୰࡟ఫࡳ╔࠸࡚࠸ࡿࡶࡢࡶ࠸ࡿࠋᑠ➟ཎ࡛ࡣ㒓ᅵᩱ⌮࡟ࡶ࡞ࡗ࡚࠸ࡿࡋࠊࢲ
࢖ࣂ࣮ࡸ⁺ᴗ⪅ࡢ୰࡟ࡣࠊ
ࠕẖ᪥ぢ࡚࠸ࡿࡼࠖ࡜ゝ࠺ேࡉ࠼࠸ࡿࠋሙᡤࡉ࠼㑅࡭ࡤࠊ࢔࢜࢘
࣑࣓࢞ࡣ⮬↛ࡢ୰࡛ࡶฟ఍࠼ࡿື≀࡛࠶ࡿࠋࡇࡢࡼ࠺࡟࢔࣑࢜࢘
࣓࢞ࡣඃ㞞࡛ேẼ⪅ࠊࡑ
ࡋ࡚㌟㏆࡞ື≀࡜࠸࠼ࡿࠋᮏ❶࡛ࡣࠊࡇࡢ࢔࢜
࣑࣓࢘࢞ࡀ࡝ࡢࡼ࠺࡞
ື≀࡛ࠊ࡝ࡢࡼ࠺࡞୍⏕ࢆ㐣ࡈࡍ࠿ࢆ⤂௓ࡋࡓ࠸ࠋᢂපẴỦỴỼỸἱỾἳ Swimming green turtle

3Chapter One: An Overview of the Green Turtle
Kazunari Kameda

Introduction
Anyone who has been scuba diving in Okinawa has probably seen a green turtle. The
green turtle moves its flipper like a bird, and is a graceful swimmer. They have smallhead, big eyes, and streamlined carapace shape, and are said to be the most charismaticof sea turtle species. Sea turtles are popular in aquariums and green turtle hatchlings are
the most loved by tourists.
The green turtle is one of seven sea turtle species. The Japanese name for green
turtles is ao-umigame but they are also referred to as asahigame, shogakubo, andmijiga-mi. They inhabit warm coastal waters and encounter human beings more thanother sea turtle species. In Hawaii, green turtles are known to bask in the sun andtourists often find sea turtles resting close to them. For those living in urban areas, green
turtles may only be seen at aquariums. However, they can be encountered often in someregions of Japan. In Amami and Okinawa, green turtles can be seen from the shore andsomePeopleliveinlivingharbors.
inOgasawaratheIslands

consume green turtles as acultural cuisine. There aredivers and fishermen who
spot green turtles everyday. In this chapter, thebehavior of the green
turtle and its life cycle
will be introduced.
ỴỼỸἱỾἳỉ‫܇‬Ỿἳᴾ Juvenile green turtleᴾ4‫ࡢ࣓࣑࢞࢘࢜࢔ە‬యࡢ≉ᚩ ࣑࣓࢘࢞ࡣࡶ࡜ࡶ࡜㝣ᆅ࡟ఫࢇ࡛࠸ࡓ࣓࢝ࡀᾏ࡟㐍ฟࡋࡓࡶࡢ࡛࠶ࡿࠋᾏ୰࡜࠸࠺⎔ቃ࡟࠶ࢃࡏ࡚ࠊయࡢࡉࡲࡊࡲ࡞㒊ศࡀ㐍໬ࡋࡓࠋᾏࡢ୰࡛㏿ࡃὋࡄࡓࡵ࡟ࠊ⫥ࡢᣦࡣ㛗ࡃ࡞ࡾ⯪ࡢ࣮࢜ࣝࡢࡼ࠺࡟࡞ࡗࡓࠋᾏ࡛ࡣ⏥ࡽ࡟㛢ࡌࡇࡶࡿࡼࡾࡶࠊ⣲᪩ࡃὋ࠸࡛㏨ࡆࡓ᪉ࡀ⏕ࡁṧࡿࡇ࡜ࡀ࡛ࡁࡓࡵࠊ࣑࣓࢘࢞ࡣ⏥ࡽࡢ୰࡟ධࡽ࡞ࡃ࡞ࡗࡓࠋᾏ࡛ࡣᾋຊ࡟ࡼࡗ࡚య
ࡀᨭ࠼ࡽࢀࡿࡓࡵࠊ㝣ୖࡼࡾࡶయࢆ኱ࡁࡃࡍࡿࡇ࡜ࡀ࡛ࡁࡓࠋࡑࢀ࡟ᾏࡣ୍ࡘ࡛ࠊࡍ࡭࡚
ࡀ⧅ࡀࡗ࡚࠸ࡿࡢ࡛⏕ᜥᆅࢆᗈࡆࡿࡇ࡜ࡀᐜ࡛᫆࠶ࡗࡓࠋᐇ㝿࡟࣑࣓࢘࢞㢮 7 ✀ࡢ࠺ࡕ࢔࣑࣓࢝࢘࢞ࠊࢱ࢖࣐࢖ࠊ࢜ࢧ࣓࢞ࠊࣄ࣓࣑࣓࢘࢞ࡑࡋ࡚࢔࣑࣓࢜࢘࢞ࡢ 5 ✀ࡣࠊୡ⏺୰ࡢᾏ࡟⏕ᜥࡋ࡚࠸ࡿࠋ ࢔࣑࣓࢜࢘࢞ࡣࠊ࣑࣓࢘࢞㢮ࡢ୰࡛ࡣ࢜ࢧ࣓࢞ࡢḟ࡟኱ࡁࡃ࡞ࡿ✀㢮࡛࠶ࡿࠋ኱すὒࡢ࢔ࢭࢩࣙࣥᓥ࡛ࡣ⏥ࡽࡢ㛗ࡉࡀ 139 cm ࡢグ㘓ࡀ࠶ࡿࠋࡇࢀࡔࡅᕧ኱࡞ࡶࡢࡣ౛እⓗ࡛࠶ࡿࡀࠊ⏘༸࡟ゼࢀࡿẕ࣓࢞ࡣ⏥ࡽࡢ㛗ࡉࡀ 1m ௨ୖࡢࡶࡢࡶ⌋ࡋࡃ࡞࠸ࠋ࡞࠾ࠊ࣓࢝㢮ࡣ㢌ࡀ⏥ࡽ࡟ᘬࡗ㎸ࢇ࡛ࡋࡲ࠺ࡓࡵ඲㛗ࡀࡾ࡟ࡃ࠸ࠋࡇࡢࡓࡵ࣓࢝ࡢ኱ࡁࡉࡣ⏥ࡽࡢ㛗ࡉࢆᇶ‽࡜ࡋ࡚࠸ࡿࠋ
࢔࣑࣓࢜࢘࢞ࡢ㢌ࡣᑠࡉࡃ࡚୸࠸ࠋࡇࢀࡣࠊ࢔࣑࣓࢜࢘࢞ࡀ࣑࣓࢘࢞㢮ࡢ୰࡛ࡣ၏୍ࡢ
ⲡ㣗࡛ࠊ኱ࡁ࠸䭱ࢆ୸࿐ࡳࡋࡓࡾࠊ࢚ࣅ࣭࢝ࢽ࡞࡝ࡢሀ࠸Ẇࢆᣢࡘື≀ࢆ㣗࡭ࡓࡾࡋ࡞࠸
ࡓࡵ࡛࠶ࡿࠋࡑࡢ௦ࢃࡾࠊཱྀ࡟ࡣࢠࢨࢠࢨ࡜ࡋࡓ✺㉳ࡀ࠶ࡾࠊࡃࢃ࠼ࡓᾏⲡࡀ⁥ࡽ࡞࠸ࡼ࠺࡟࡞ࡗ࡚࠸ࡿࠋࡘࡲࡾࠊ࣌ࣥࢳ࡟ࡘ࠸࡚࠸ࡿพฝ࡜ྠࡌᙺ๭࡛࠶ࡿࠋ࢔࣑࣓࢜࢘࢞ࡣࡇ
ࡢཱྀ࡛ᾏⲡࢆࡃࢃ࠼࡚ࠊࡕࡂࡗ࡚㣗࡭࡚࠸ࡿࠋ
࢔࣑࣓࢜࢘࢞ࡢ⏥ࡽࡣୖ࠿ࡽぢࡿ࡜ᴃ෇ᙧࢆࡋ࡚࠸ࡿࠋ୍᪉ࠊ࢔࣑࣓࢝࢘࢞ࡸࣄ࣓࣑࢘
࣓࢞࡞࡝ࡣ⏥ࡽࡀ㏫୕ゅᙧࢆࡋ࡚࠸ࡿࠋ୍⯡࡟ࠊື≀㉁ࡼࡾࡶ᳜≀㉁ࡢ䭱ࡢ᪉ࡀᾘ໬࡟᫬
㛫ࡀ࠿࠿ࡿࠋࡇࡢࡓࡵ⫗㣗ື≀ࡼࡾࡶࠊⲡ㣗ື≀ࡣ⭠ࡀ㛗ࡃ࡞ࡿഴྥ࡟࠶ࡿࠋ࢔࣑࢜࢘࢞
࣓ࡢ⏥ࡽࡀᴃ෇ᙧ࡞ࡢࡣࠊⲡ㣗࡛࠶ࡿࡓࡵ࡟௚ࡢ࣑࣓࢘࢞㢮ࡢࡼࡾࡶ⭠ࡀ㛗ࡃࠊࡑࡢ⭠ࢆ཰ࡵࡿࡓࡵ࡟ᗈ࠸✵㛫ࡀᚲせࡔ࠿ࡽ࡜⪃࠼ࡽࢀ࡚࠸ࡿࠋ
⏥ࡽࡢⰍࡸᶍᵝࡣಶయᕪࡀ࠶ࡗ࡚ࠊ㉥ࡀ⃰࠸ࡶࡢࡸ㯮ࡗࡱ࠸ࡶࡢ࡞࡝ࠊࡉࡲࡊࡲ࡛࠶ࡿࠋ
ഴྥ࡜ࡋ࡚ࡣࠊࡩ໬ࡋࡓ᫬ࡣ㯮ࡃࠊ1 ṓࡄࡽ࠸࡛㉥ࡃ࡞ࡾࠊࡑࡢᚋࡣⲔⰍࠊ㯮࡜ࡉࡲࡊࡲ࡞
Ⰽࡀΰࡌࡿࡼ࠺࡟࡞ࡾࠊᡂ⇍ࡋࡓぶ࣓࢞ࡣ㯮࠸ࡶࡢࡀከ࠸ࠋࡲࡔᡂ⇍ࡋ࡚࠸࡞࠸ⱝ࠸࢔࢜
࣑࣓࢘࢞࡟ࡣࠊ⏥ࡽࡢ㫣ࡢ୍ᯛ୍ᯛ࡟ᮅ᪥ࡢࡼ࠺࡞ᶍᵝࡀ࠶ࡿࠋࡇࡢᮅ᪥ᆺࡢᶍᵝࡣࠊᡂ㛗ࡍࡿ࡜ᑡࡋࡎࡘࡰࡸࡅ࡚ࡋࡲ࠺ࠋኴᖹὒࡢᮾ㒊࡟ࡣࠊࢡ࣑࣓ࣟ࢘࢞࡜࠸࠺࣑࣓࢘࢞ࡀ⏕ᜥࡋ࡚࠸ࡿࠋࢡ࣑࣓ࣟ࢘࢞ࡣ࢔࣑࣓࢜࢘࢞࡜㠀ᖖ࡟ࡼࡃఝ࡚࠸ࡿࡀ⏥ࡽࡢᙧࡀᑡࡋ␗࡞ࡾࠊ
ఱࡼࡾࡶయࡢ඲యࡀ㯮࠸ࠋࡇࡢࢡ࣑࣓ࣟ࢘࢞࡟ࡘ࠸࡚ࡣ➨ 3 ❶࡛ヲࡋࡃㄝ᫂ࡍࡿࠋ

5

Physical features
Sea turtles were once terrestrial reptiles and have since moved into the sea. Theirbodies have changed to adapt to the oceanic environment. Their phalanges grew longer
to form a paddle-like shape to swim faster in water. Sea turtles are able to escape byswimming rather than withdrawing their body parts into their shell like their terrestrial
cousins. The buoyant forces supporting the weight of the body enabled sea turtles togrow larger in water than on land. Sea turtles were also able to expand their habitats bytraveling throughout the ocean. Out of the seven species of sea turtle, the loggerhead
turtle, hawksbill turtle, leatherback turtle, and Kemp’s ridley turtle inhabit the sea
extensively around the world.
The green turtle is the second largest sea turtle: first being the leatherback turtle. A
green turtle with carapace length of 139 cm was seen on Ascension Island. Finding agreen turtle of this size is exceptional, but turtles coming ashore to nest are usuallylarger than 1 m. Turtles draw back into its shell when threatened and it is difficult tomeasure the total length. Therefore, carapace length is used to determine turtle size.
The head of green turtle is round and small since it is a herbivore and does not forage
on large prey. The mouth is similar to pliers, and is equipped with projecting teeth,
which help it to get a good grip on the food. Green turtles use this projection to grasp
and tear seaweed.
The shape of the green turtle’s carapace is an oval. In contrast, the shape of theloggerhead and Kemp’s ridley carapace is similar to an inverted triangle. Digesting
vegetable matter takes more time than digesting animal matter. Therefore, the intestinesof herbivorous animals are longer than those of carnivorous animals. Since green turtles
are herbivorous, their intestines are longer than those of other sea turtle species and theiroval carapace shape is essential for storing long intestines.
Carapace colors vary among individuals. Many colors, such as dark red and black, arefound among green turtles with the same carapace size. Green turtle hatchlings are black,and turn reddish around one year of age. Brown and black colors mix with red and the
majority of mature green turtles are black. Color rays that look like the rising sun can beseen on the scale of juvenile green turtles; however, this pattern fades as green turtles
grow. Mature black turtles, found on the eastern side of Pacific Ocean, is similar to the6ỴỼỸἱỾἳỉဍỤỊ̾˳ỆợẾề‫ݲ‬Ẳẵếᑥể೉ಮầီễỦᴾ
Color patterns of immature green turtle‫⏘ࡢ࣓࣑࢞࢘࢜࢔ە‬༸⾜ືᾏࡢ୰࡛ࡢ⏕ά࡟㐺ᛂࡋࠊ⏕ᜥᇦࢆᗈࡆࡓ࣑࣓࢘࢞㢮࡛࠶ࡿࡀࠊ༸ࡔࡅࡣ㝣ୖ࡛ࡋ࠿Ꮴ
໬࡛ࡁ࡞࠿ࡗࡓࠋࡇࡢࡓࡵẕ࣓࢞ࡣ༸ࢆ⏘ࡴࡓࡵ࡟◁὾࡟ୖ㝣ࡍࡿࠋ࣑࣓࢘࢞ࡢ⏘༸ࡣࠊኪ㛫࡟ேࡢẼ㓄ࡢ࡞࠸࡜ࡇࢁ࡛⾜ࢃࢀࡿࡓࡵࠊᐇ᪋࡟ぢࡿࡇ࡜ࡣ㞴ࡋ࠸ࠋࡋ࠿ࡋࠊ⏘༸ࡢࡓࡵ࡟ୖ㝣ࡋࡓ⑞㊧࡞ࡽࠊ᪥୰࡟ࡶぢࡿࡇ࡜ࡀฟ᮶ࡿࠋ࣑࣓࢘࢞ࡀୖ㝣ࡍࡿ࡜ࠊ◁὾࡟ᖜ
1m ࡯࡝ࡢ࢟ࣕࢱࣆࣛࡢࡼ࠺࡞㊊㊧ࡀࠊᾏ࠿ࡽ㝣ᆅ࡟ྥ࠿ࡗ࡚⥆࠸࡚࠸ࡿࠋୖ㝣ࡋࡓ࢔࢜࢘
࣑࣓࢞ࡣࠊ୧᪉ࡢ๓㊊ࢆྠ᫬࡟๓࡟ฟࡋ࡚๓㐍ࡍࡿࠋỈὋࡢࣂࢱࣇࣛ࢖ࡢࡼ࠺࡞ឤࡌ࡛࠶
ࡿࠋࡇࡢࡓࡵ࢔࣑࣓࢜࢘࢞ࡢୖ㝣ࡢ⑞㊧ࡣࠊᕥྑࡢ㊊㊧ࡀᖹ⾜࡟࡞ࡿࠋ࢔࣑࣓࢝࢘࢞ࡸࢱ
࢖࣐࢖ࡣ๓㊊ࢆ஺஫࡟ື࠿ࡋ࡚ࢡ࣮ࣟࣝࡢࡼ࠺࡟㐍ࡴࡢ࡛ࠊ࢔࣑࣓࢜࢘࢞ࡢ㊊㊧࡜༊ูࡍࡿࡇ࡜ࡀ࡛ࡁࡿࠋ

7

green turtle but differs in color and in the shape of the carapace. Details of black turtles
will be introduced in chapter three.

ỴỼỸἱỾἳỉӝẇἬὅἓỉợạễЇІầẝụẆෙᕹửẪỪảềờ๖ỤễẟợạỆễẾềẟỦᴾ
The mouth of green turtle is similar to pliers. Projecting teeth are aligned in alternating manner. This feature
helps green turtle get a tight hold of sea algae when foraging.

Nesting habits of the green turtle
Sea turtles adapted to oceanic environments and were able to extend their range,
however, turtle eggs are only able to hatch on land. Mother turtles still come ashore to
nest. Sea turtle nesting takes place at night when there are no signs of humans.
Therefore, it is difficult to observe nesting behavior. On the other hand, tracks left onbeaches by mother turtles can be seen in daylight. Turtle tracks are about one meterwide and are similar to prints left by tractors. Green turtles move both of their front8ୖ㝣ࡋࡓ㊊㊧ࡢඛ࡟ᖜ 1.5m ࡯࡝ࡢ✰ࡀ࠶ࡾࠊࡑࡢᚋࢁࡢ◁ࡀ┒ࡾୖࡀࡗ࡚࠸ࢀࡤࠊ⏘༸ࡋ࡚࠸ࡿྍ⬟ᛶࡀ㧗࠸ࠋ࡞ࡐ࡞ࡽࠊࡑࡢ┒ࡾୖࡀࡾࡣẕ࣓࢞ࡀ༸ࢆ⏘ࡳⴠ࡜ࡋࠊࡑࢀࢆ㞃ࡍࡓࡵ࡟◁ࢆ࠿ࡅࡓドᣐࡔ࠿ࡽ࡛࠶ࡿࠋ
࢔࣑࣓࢜࢘࢞ࡢ⏘༸ࡣࠊ᪥୰ࡢᙉ࠸᪥ᕪࡋࢆ㑊ࡅ࡚ኪ㛫࡟࠾ࡇ࡞ࢃࢀࡿࠋ⮬↛ࡢ◁὾ࡣࠊᾏ࠿ࡽ◁὾࡟⥆ࡁࠊࡑࡋ࡚ᾏ὾᳜≀࡬࡜⧅ࡀࡗ࡚
࠸ࡿࠋୖ㝣ࡋࡓ࢔࣑࣓࢜࢘࢞
ࡣ◁὾ࡢ◁ࡀษࢀࡿ࡜ࡇࢁࠊ
ࡘࡲࡾᾏ὾᳜≀ࡢ࡜ࡇࢁࡲ
࡛⛣ືࡍࡿࠋࡑࡇ࡛๓㊊ࢆࡘ࠿ࡗ࡚✰ࢆ᥀ࡾࠊయࡢ඲యࢆ
ᑡࡋᇙࡵࡿࠋࡇࡢ✰ࡣ࣎ࢹෙỆ৏ỦỴỼỸἱỾἳẇᴾ
ငҳỉẺỜỆỊɥᨕẲễẬủịẟẬễẟᴾ
Green turtle returning to the sea after nesting:࢕࣮ࣆࢵࢺ࡜࿧ࡤࢀࠊ⏘༸ᚋࡣ┤ᚄ 1m ࡯࡝ࡢ✰࡜ࡋ࡚ṧࡿࠋࡑࢀ࠿ࡽᚋࢁ㊊ࢆit must come ashore to spawn.

౑ࡗ࡚༸ࢆ⏘ࡴࡓࡵࡢ✰ࢆ࡯ࡿࠋ✰ࡣ῝ࡉ 60 ੉࡯࡝ࡲ࡛᥀ࡾࠊ100 ಶ࡯࡝ࡢ༸ࢆ⏘ࡳⴠ࡜ࡍࠋ༸ࢆ⏘ࡳ⤊࠼ࡿ࡜ᚋࢁ
㊊࡛✰ࢆᇙࡵࠊࡉࡽ࡟๓㊊ࢆ౑ࡗ࡚༸ࢆ⏘ࢇࡔ࿘㎶࡟◁ࢆ࠿ࡅࡿࠋࡑࢀ࠿ࡽࡼ࠺ࡸࡃᾏ࡟
ᡠࡿࠋୖ㝣ࡋ࡚࠿ࡽ⏘༸ࡋ࡚ᾏ࡟ᖐࡿࡲ࡛ࠊᬑ㏻ࡣ 2 ᫬㛫࠿ࡽ 3 ᫬㛫࠿࠿ࡿࠋ⏘༸ࡢࡓࡵ࡟ୖ㝣ࡋࡓẕ࣓࢞ࡣࠊ࡜࡚ࡶ⚄⤒㉁࡟࡞ࡗ࡚࠸࡚༴㝤ࢆឤࡌࡿ࡜ࡍࡄ࡟ᾏ࡟
ᡠࡗ࡚ࡋࡲ࠺ࠋ㉥࠸ගࡣ࣓࢝࡟ࡣぢ࠼࡞࠸࡜࠸࠺ヰࡀ࠶ࡾࠊ㉥࠸ࣛ࢖ࢺ࡞ࡽ࣑࣓࢘࢞ࢆ↷ࡽࡋ࡚ࡶ኱୔ኵ࡜⪃࠼࡚࠸ࡿேࡀ࠸ࡿࠋࡋ࠿ࡋࠊ࡝ࡢⰍࡀぢ࠼ࡿ࠿ࡣ࣑࣓࢘࢞ࡢ✀㢮࡟ࡼࡗ࡚㐪࠺ࠋ࢔࣑࣓࢜࢘࢞ࡣ㉥Ⰽࢆឤࡌࡿࡇ࡜ࡀ࡛ࡁࡿࡢ࡛ࠊ㉥࠸ࣛ࢖ࢺ࡛↷ࡽࡍ࡜㦫࠸࡚ᾏ࡟ᡠࡗ࡚ࡋࡲ࠺ࠋேࡀ㦫࠿ࡉ࡞ࡃ࡚ࡶࠊ࣑࣓࢘࢞ࡣ⏘༸ࡋ࡞࠸ࡇ࡜ࡀ࠶ࡿࠋ౛࠼ࡤࠊ༸
ࢆ⏘ࡴࡓࡵࡢ✰ࢆ᥀ࡗ࡚࠸ࡿ᫬࡟ᒾ࡟࠶ࡓࡗࡓࡾࠊ◁ࡀ஝࠸࡚ᔂࢀࡸࡍ࠸࡜༑ศ࡞῝ࡉࡲ࡛✰ࢆ᥀ࢀ࡞࠸ࡢ࡛⏘༸ࡏࡎ࡟ᾏ࡟ᖐࡗ࡚ࡋࡲ࠺ࠋࡑࢀ࡟ࠊே࠿ࡽぢࢀࡤ࡜࡚ࡶ⏘༸࡟㐺ࡋࡓ࡜ࡇࢁ࡞ࡢ࡟ࠊᩘ᫬㛫ࡶ◁὾ࢆ⛣ືࡋ⥆ࡅ࡚ࠊ✰ࢆ᥀ࢁ࠺࡜ࡶࡏࡎ࡟ᖐࡿࡇ࡜ࡶ࠶ࡿࠋ

9

flippers at the same time, similar to the ‘butterfly stroke’ of human swimmers, andtracks left by the right and left front flippers are parallel. Loggerhead turtles andhawksbill turtles move their front flippers alternately like ‘free-style’ swimmers so theirtrackscanbedistinguished from thoseof green turtles. There is ahigh possibility of finding
sea turtle nests if a pile ofsand 1.5 meter in diameter
is found at the end of
turtle tracks. The sand pileis a evidence that a motherturtle covered her nest
with sand to hide it frompredators.

ỴỼỸἱỾἳỉငҳၕួ Nesting trace ofgreen turtle

Green turtle nesting takes place at night to avoid strong sunshine. The beach is
divided in to sand and sea side plant zone. . When mother turtles proceed inland, theycrawl on sand until they reach the area where seaside plants grow. They use their front
flippers to dig a hole and slightly bury their body in sand. This hole is referred to as a‘body pit’ and remains as a hole one meter in diameter after nesting. After digging with
their front flippers, anterior flippers are used to dig a deeper hole. The depth of this holeis about 60 cm and is used to lay eggs. In each nesting, about one hundred eggs are laid.
This hole is covered with sand using the anterior flippers, and the front flippers are used
to camouflage the nesting area. The nesting process takes an average of two to threehours to complete.
Female sea turtles coming ashore to lay their eggs are extremely sensitive. They
return to the sea when danger is detected. Few of the sea turtle species cannot detect red
light. Therefore, some assume that red light can be used to search for all species ofnesting sea turtles. However, green turtles can see red light: when they are exposed, theyescape to the sea without nesting. Additional factors such as rocks and dry sand prevent10ỴỼỸἱỾἳỉငҳẇᵒᶁᶋ ỉҳử ᵏᵎᵎ ̾ỖỄငỚᓳểẴᴾ
Spawning of green turtle. The egg is about 4 cm in diameter, and green turtle lays about 100 of those ineach nesting.

‫⏕୍ࡢ࣓࣑࢞࢘࢜࢔ە‬࢔࣑࣓࢜࢘࢞ࡢ⏘༸ࡣࠊ୺࡟ኟሙ࡟⾜ࢃࢀࡿࠋ᪥ᮏ࡛ࡢ⏘༸ᮇࡣ 4 ᭶࠿ࡽ 9 ᭶ࡲ࡛ࠊࣆ
࣮ࢡࡣ 7 ᭶࡛࠶ࡿࠋ࢔࣑࣓࢜࢘࢞ࡣ୍ᗘࡢ⏘༸࡛ 100 ಶ࡯࡝ࡢ༸ࢆ⏘ࡴࠋࡇࢀࢆ୍ᖺ㛫࡟⣙ 2 㐌㛫ࡢ㛫㝸࡛ 4 ᅇࡄࡽ࠸⏘༸ࡍࡿࠋࡑࡋ࡚ࠊࡑࡢᖺࡢ⏘༸ࡀ⤊ࢃࡿ࡜ḟࡢ⏘༸ࡣ 3 ᖺ
࠿ࡽ 4 ᖺᚋ࡛ࠊ࡯࡜ࢇ࡝ྠࡌ◁὾࡟ᡠࡗ࡚ࡃࡿࠋ౛࠼ࡤࠊ7 ᭶ 1 ᪥࡟㯮ᓥࡢすࡢ὾࡛⏘༸ࡀ࠶ࢀࡤࠊࡑࡢᚋ 2 㐌㛫ᚋ࡛࠶ࡿ 7 ᭶ 15 ᪥ࡈࢁ࡟෌ࡧすࡢ὾࡟ୖ㝣ࡍࡿࠋࡑࡋ࡚ 8 ᭶ 1 ᪥ࡈࢁ࡟෌ࡧすࡢ὾࡟ୖ㝣ࡋ࡚࣭࣭ࠊ࡜⏘༸ࢆ⧞ࡾ㏉ࡍࡢ࡛࠶ࡿࠋࡑࡋ࡚ 3 ᖺ࠿ 4 ᖺᚋ࡟෌ࡧすࡢ὾࡟ୖ㝣ࡋ࡚ࠊࡸࡣࡾ 2 㐌㛫ࡈ࡜࡟ 4 ᅇ࡯࡝⏘༸ࡍࡿࠋࡇࡢ⏘༸࡟ᡠࡗ࡚ࡃࡿᖺ࿘ᮇ
ࡣᆅᇦ࡟ࡼࡗ࡚␗࡞ࡾࠊ౛࠼ࡤ࣮࢜ࢫࢺࣛࣜ࢔ࡢࣞ࢖ࣥᓥ࡛ࡣᖹᆒ 5 ᖺ࡛ᡠࡗ࡚ࡃࡿࠋ୍
᪉࡛ࠊỈ᪘㤋࡛ࡣẖᖺ⏘༸ࡍࡿẕ࣓࢞ࡶ࠸ࡿࡇ࡜࠿ࡽࠊࡇࡢ⏘༸࡟ᡠࡗ࡚ࡃࡿᖺ࿘ᮇࡣ࠾
ࡑࡽࡃᾏỈ ࡸẕ࣓࢞ࡢᰤ㣴ࡢ≧ែ࡟ࡼࡗ࡚ኚࢃࡗ࡚ࡃࡿࠋ
⏘ࡳⴠ࡜ࡉࢀࡓ༸ࡣ 4 ੉ࡄࡽ࠸࡛ⷧ࠸ⲔⰍࢆࡋ࡚࠸ࡿࠋ༸ࡢẆࡣࡸࢃࡽ࠿ࡃࠊ⏘ࡳⴠ࡜ࡉࢀࡓ࡜ࡁพࡴࡶࡢࡀከ࠸ࠋⷧⲔⰍࡢ༸ࡣୖࡢ᪉࠿ࡽᚎࠎ࡟஝࠸࡚ⓑࡃ࡞ࡗ࡚࠸ࡁࠊ10 ᪥

11sea turtles from laying eggs and on some occasions, sea turtles have been observed
traveling along the beach for hours without digging. This happens even when the beachis suitable for nesting; however, the judge is from a human perspective.

ငҳầኳỪỦểẆჿửẦẬềҳửᨨẲềẦỤෙỆ৏Ủᴾ
After spawning, green turtles cover eggs with sand before returning to the sea.

Life cycle
Summer is nesting season for green turtles. In Japan, the season starts from April
until September and the peak is in July. Green turtles lay about one hundred eggs ineach nesting. They nest about four times each year in a two-week cycle, in once every
three to four years. Female green turtles have a high probability of returning to the same
rookery. For example, if a mother turtle nests at Nishinohama beach on KuroshimaIsland on July 1st, it will be seen nesting again around July 15th, August 1st, and August
15th on the same beach. After a season of nesting, it is likely to return to Nishinohama
beach four years later, to spawn again in a two-week cycle. The nesting trend depends
on the rookeries. For example, green turtles return to Raine Island, Australia in an

12࡯࡝࡛඲యࡀⓑࡃ࡞ࡿࠋ⏘ࡳⴠ࡜ࡉࢀࡓ┤ᚋࡢ༸ࡢୖୗࢆኚ࠼࡚ࡶ኱୔ኵ࡛࠶ࡿࡀࠊ24 ᫬㛫௨ୖࡓࡗࡓ࠶࡜ࡣୖୗࢆኚ࠼ࡿ࡜ࠊⓎ⏕ࡀṆࡲࡗ࡚ࡋࡲ࠸Ꮴ໬ࡋ࡞ࡃ࡞ࡿࠋ༸ࡣ⣙ 2 ࣨ᭶ᚋ࡟Ꮴ໬ࡍࡿࠋࡇࡢ༸ࡀᏤ໬ࡍࡿࡲ࡛ࡢ

ᗘ࡟ࡼࡗ࡚ࠊࡑࡢ࢔࣑࣓࢜࢘࢞ࡢᛶูࡀỴࡲࡿࠋ࠾࠾ࡼࡑ 29 ᗘࡼࡾࡶపࡅࢀࡤ࢜ࢫ࡟࡞ࡾࠊ㧗ࡅࢀࡤ࣓ࢫ࡟࡞ࡿࠋ
ࡩ໬ࡋࡓᏊ࣓࢞ࡣ⏥ࡽࡢ㛗ࡉࡀ 5 ੉࡯࡝࡛ࠊ⫼୰ഃࡣ㯮ࡗࡱ࠸Ⰽࢆࡋ࡚ࠊ࠾⭡ࡣ┿ⓑ࡛࠶ࡿࠋᏊ࣓࢞ࡣࡩ໬ࡋ࡚࠿ࡽᩘ᪥ࡣ◁ࡢ୰࡟࠸ࡿࠋ◁὾࠿ࡽࡢ⬺ฟࡢࢱ࢖࣑ࣥࢢࡣࠊኪ㛫࡟◁ࡢ ᗘࡀୗࡀࡗࡓࡇ࡜ࡀྜᅗ࡟࡞ࡿࠋᏊ࣓࢞ࡓࡕࡣ୍ᩧ࡟◁࠿ࡽ⬺ฟࡋᾏ࡬࡜ྥ࠿࠺ࠋ
◁὾ࡢഴᩳࡣ㝣ᆅࡀ㧗ࡃࠊᾏ࡟ྥ࠿ࡗ࡚పࡃ࡞ࡗ࡚࠸ࡿࠋேᕤࡢ᫂࠿ࡾࡀ࡞࠸⮬↛ࡢ◁὾ࡣࠊᾏࡢ᪉ࡀ᫂ࡿࡃ࡚ࠊ㝣ࡢ᪉ࡀᬯ࠸ࠋ≉࡟ᾏ὾᳜≀ࡀ㇏࠿࡞࡜ࡇࢁࡣࠊࡑࡢ᳜≀ࡀ㝜࡟࡞ࡿࡢ࡛ࡼࡾ࠸ࡗࡑ࠺㝣ഃࡀᬯࡃ࡞ࡿࠋᏊ࣓࢞ࡣ◁὾ࡢప࠸᪉࡟ྥ࠿ࡗ࡚㐍ࡳࠊࡑࡢᚋࡣ
᳜≀ࡢᙳ࡜᫂ࡿࡉࢆࡓࡼࡾ࡟ࡋ࡚ࠊᾏࡢ᪉ྥࢆぢࡘࡅࡿࠋࡑࡋ࡚ᾏ࡟ࡓ࡝ࡾࡘ࠸ࡓᏊ࣓࢞
ࡣࠊἼࡢ᪉ྥ࡟㏫ࡽ࠺ࡼ࠺࡟ࡋ࡚Ἀࢆ┠ᣦࡋ࡚Ὃ࠸࡛⾜ࡃࠋࡇࡢ◁὾࠿ࡽ⬺ฟࡋࠊᾏ࡟ࡣ
࠸ࡗ࡚Ἴ࡟㏫ࡽࡗ࡚Ὃࡄ㛫࡟ࠊᆅ⌫ࡢ☢ሙࢆឤ▱ࡍࡿ⬟ຊࢆ㌟࡟ࡘࡅࡿࠋࡘࡲࡾࠊయࡢ࡞
࠿࡟ࢥࣥࣃࢫࢆᣢࡘࡢ࡛࠶ࡿࠋࡇࡢ⬟ຊ࡟ࡼࡗ࡚ࠊ࢔࣑࣓࢜࢘࢞ࡣ㝣ᆅࡢぢ࠼࡞࠸኱ὒ࡛ࡶ᪉ྥࢆぢኻ࠺ࡇ࡜࡞ࡃ⏕ά࡛ࡁࡿࠋ

ᴾ‫܇‬ỾἳỊɟ૪ỆჿẦỤᏮЈẲẆෙồểӼẦạᴾ
Turtle hatchlings crawl out of clutches and head to the sea in a group.

13average of every five years. Mother sea turtles bred in captivity nest almost every year.
Therefore, nesting trends may vary depending on seawater temperatures and nutrition.
Freshly laid eggs are about 4 cm in diameter and are light brown colored. Shells aresoft and often dented when laid. The light brown color gradually turns to white as they
dry from the top of the egg. The drying process usually takes about 10 days. The egg
can be turned when laid;
however, if it is turned
upside-down

after

24

hours, the embryo stops
developing. In about twomonths, hatchlings crawl
out. Sex determination ofgreen

turtlesistemperature dependent. If
the clutch temperature islower than 29q C, maleỐ҄ႺࢸỉỴỼỸἱỾἳẇဍỤỉᧈẰỊ ᵓ ὬỖỄᴾ
Baby green turtle just after hatching. The carapace length is about 5 cm.

turtles, while if over 29q
C, female turtles hatch.
Hatchlings

have

a

carapace length of about 5 cm. The upper shell is blackish, while the plastron is white.
Newly born hatchlings remain in the sand for the first few days. When sandtemperatures drop at night, hatchlings emerge from clutches and head towards the sea.
The altitude of the beach is higher in-land and gradually decreases towards the sea.
Under natural conditions, the ocean at night is brighter than the land. Land with
abundant seaside plants is especially dark. Sea turtle hatchlings descend the slope andhead towards the brighter sea. Once in the water, they swim against the waves towards
deeper water. Hatchlings gain ability to sense the magnetic field of the earth during theirfirst swim. Green turtles can keep their bearings even in pelagic waters by using thisinternal body compass.

14 Ꮚ࣓࢞ࡣ 24 ᫬㛫࠿ࡽ 36 ᫬㛫ࡣࡦࡓࡍࡽἈ࡟ྥ࠿ࡗ࡚Ὃࡄࠋࡇࢀࡀࣇࣞࣥࢪ࣮࡜ゝࢃࢀࡿ⯆ዧ≧ែ࡛ࠊ䭱ࡶ㣗࡭ࡎ࡟ࡦࡓࡍࡽὋࡂ⥆ࡅࡿࠋᏊ࣓࢞ࡣࡇࡢࣇࣞࣥࢪ࣮ࡢ᫬࡟ࠊἢᓊ
࠿ࡽ㞳ࢀࠊእὒ࡛ࡢ⏕άࢆࡣࡌࡵࡿࠋᐇࡣࠊእὒ࡛ࡢ⏕άࢆጞࡵࡓᏊ࣓࢞࡟ฟ఍࠺ࡇ࡜ࡣ
⁛ከ࡟࡞࠸ࠋḟ࡟ฟ఍࠺ࡢࡣࠊ⏥ࡽࡢ㛗ࡉࡀ 35cm ࠿ࡽ 40 ੉࡟࡞ࡗ࡚ࠊἢᓊ࡛ࡢ⏕άࢆࡣࡌࡵ࡚࠿ࡽ࡛࠶ࡿࠋࡘࡲࡾࠊࢲ࢖ࣅࣥࢢࢆࡋ࡚࠸࡚ 35 ੉௨ୗࡢ࢔࣑࣓࢜࢘࢞ࢆぢ࠿ࡅࡿࡇ࡜ࡣ࡞࠸ࠋእὒ࡛⏕άࡋ࡚࠸ࡿᏊ࣓࢞ࡣࠊ࠾ࡑࡽࡃ⁻ὶ≀࡜୍⥴࡟࠸ࡿ࡜ゝࢃࢀ࡚࠸ࡿࡀࠊ
ぢࡘ࠿ࡗࡓ౛ࡣࡈࡃࢃࡎ࠿࡛࠶ࡿࠋ࡞࠾ࠊ኱すὒࡢ࢔࣑࣓࢜࢘࢞ࡣ⏥ࡽࡢ㛗ࡉࡀ 25cm ࡯࡝ࠊኴᖹὒ⏘ࡼࡾࡶᑠࡉ࠸࡜ࡁ࠿ࡽἢᓊ࡛ࡢ⏕άࢆࡣࡌࡵࡿࡇ࡜ࡀ▱ࡽࢀ࡚࠸ࡿࠋ
ἢᓊ࡛ࡢ⏕άࢆࡣࡌࡵࡓ࢔࢜࢘
࣑࣓࢞ࡣࠊᾏⲡࡸᾏ⸴ࢆ㣗࡭࡚ᡂ㛗ࡍࡿࠋࡑࡋ࡚ࠊ20 ᖺ࠿ࡽ 40 ᖺࢆ࠿ࡅ࡚⏥ࡽࡢ㛗ࡉࡀ 80 ੉࠿ࡽ
90 ੉࡟࡞ࡾ⦾Ṫ࡟ຍࢃࡿࡼ࠺࡟࡞
ࡿࠋࡘࡲࡾࠊ࢜ࢫࡣ࣓ࢫ࡜஺ᑿࡍ
ࡿࡼ࠺࡟࡞ࡾࠊ࣓ࢫࡣ◁὾࡛⏘༸ࡍࡿࡼ࠺࡟࡞ࡿࠋ࢜ࢫࡣ⦾Ṫ࡛ࡁࡿࢧ࢖ࢬ࡟࡞ࡿ࡜ࠊ࣓ࢫࢆᤕࡲ࠼
ࡸࡍ࠸ࡼ࠺࡟∎ࡀෆഃ࡟᭤ࡀࡾࠊ
‫ٳ‬බဃ෇ửኳảềẆඝެဃ෇ửỊẳỜẺᒉẟỴỼỸἱỾἳᴾࡑࡋ࡚ᑿࡀ㛗ࡃ࡞ࡿࠋ࢔࣑࢜࢘࢞

Juvenile green turtle swimming in coastal water. Green turtles
change its habitat from pelagic water to shallow water as it grow.

࣓ࡢ஺ᑿࡣほᐹ౛ࡀᑡ࡞ࡃࠊ࡯࡜
ࢇ࡝ࢃ࠿ࡗ࡚࠸࡞࠸ࠋ࣑࣓࢘࢞ࡢ

஺ᑿࡣ࢜ࢫࡀ࣓ࢫࡢୖ࡟஌ࡗ࡚⾜ࢃࢀࡿࠋ஺ᑿࡀࡣࡌࡲࡿ࡜࠾஫࠸࡟Ὃࡆ࡞࠸ࡓࡵ࡟ࠊỈ㠃࡟ᾋ࠸࡚࠸ࡿࠋࡑࡋ࡚ᩘ᫬㛫ࡶ⥆ࡃࡇ࡜ࡀ࠶ࡿࠋ࢔࣑࣓࢜࢘࢞ࡢ஺ᑿࡣࠊ⏘༸ᆅࡢ㏆ࡃࡢᾏ࡛ほᐹࡉࢀ࡚࠸ࡿࠋࡇࡢࡓࡵ࢜ࢫࡣ⦾Ṫࡢ᫬ᮇ࡟࡞ࡿ࡜◁὾ࡢ㏆ࡃࡢᾏᇦ࡛࣓ࢫࡀ᮶
ࡿࡢࢆᚅࡗ࡚࠸ࡿࡢ࠿ࡶࡋࢀ࡞࠸ࠋ࣓ࢫࡣ⏕ࡲࢀࡓᆅᇦ࡟ᡠࡗ࡚⏘༸ࡍࡿࡇ࡜ࡀ▱ࡽࢀ࡚࠸ࡿࠋࡋ࠿ࡋࠊ⏕ࡲࢀࡓ◁὾࡜࠸࠺࡯࡝ཝᐦ࡛ࡣ࡞࠸ࠋ౛࠼ࡤࠊᑠ➟ཎㅖᓥࡢึᐷ὾࡛⏕ࡲࢀࡓ࢔࣑࣓࢜࢘࢞ࡣࠊぶ࣓࢞࡟࡞ࡿ࡜⦾Ṫࡢࡓࡵ࡟ᑠ➟ཎㅖᓥ࡟ᡠࡗ࡚ࡃࡿࡀࠊᚲࡎࡋ
ࡶึᐷ὾࡛⏘༸ࡍࡿࢃࡅ࡛ࡣ࡞࠸ࠋᏊ࣓࢞ࡣእὒ࡟ᗈࡃᩓࡽࡤࡗ࡚⏕άࡋ࡚࠸ࡿ࡜⪃࠼ࡽࢀ࡚࠸ࡿࡢ࡛ࠊ࡝ࡢࡼ࠺࡟ࡋ࡚⏕ࡲࢀࡓᆅᇦ࡟ᡠࡿࡇ࡜ࡀ࡛ࡁࡿࡢ࠿ࠊࡑࡢ࣓࢝ࢽࢬ࣒ࡣ
ᮍࡔ࡟ࢃ࠿ࡗ࡚࠸࡞࠸ࠋ

15

Hatchlings swim continuously for about 24 to 36 hours towards offshore waters. Thisphenomenon is referred to as ‘frenzy’ and hatchlings swim without foraging. The frenzy
brings hatchlings offshore, out towards pelagic waters. Once in a pelagic stage, they are
rarely encountered. They will not be spotted again until they begin their demersal stage
as juvenile sea turtles with a carapace length of 35 to 40 cm. Young hatchlings are
assumed to be floating with drifting sea weeds, but evidence is scarce. Green turtles
inhabiting the Pacific Ocean begin their demersal stage when they reach a carapace sizeof 35 cm, while Atlantic Ocean-inhabiting green turtles shift to their demersal stage
around a carapace size of 25 cm.
Demersal stage green turtles forage on seagrass and macroalgae. It takes about 20 to
40 years to grow to adult size. Once a carapace length of 80 cm to 90 cm has beenreached, they begin reproduction. Once male turtles mature, their claws bend inward
and their tails grow longer. Bent claws are used to cling to female turtles. Mating green
turtles are rarely observed and the details remain unclear. However, male turtles are
known to ride on the female back when coupling. They cannot swim during coupling sothey float at the surface and this goes on for a few hours. Couplings are observed at sea
near the rookery and it is hypothesized that male green turtles await females in the area
near the nesting site. Female sea turtles are known to return to the oceanic area close towhere they were born, but not necessarily the same beach. For example, green turtles
born in Hatsune beach return to beaches in Ogasawara Islands for nesting, but notnecessarily to the Hatsune beach. This mechanism of hatchlings returning to the same,or nearby, rookery also remains unclear.
Green turtles have a foraging area separate from their rookeries. Mother turtles
sometimes travel a few thousand kilometers to their nesting beaches. They remain in thenesting area during the nesting season; therefore, mother turtles are forced to starve if
there are no algae to forage on. After the nesting season, mothers swim the long
distance again to return to the foraging site.
The life span of green turtles is unknown. Loggerhead turtles, which are smaller thangreen turtles, live for about 60 to 70 years. Therefore, green turtles may live slightly
longer. However, most sea turtles are thought to die from predation or human activities
before dying of old age.

16

࢔࣑࣓࢜࢘࢞ࡣ䭱ࢆ㣗࡭ࡿᆅᇦ࡜⦾Ṫࡍࡿሙᡤࢆࢃࡅ࡚࠸ࡿࠋࡇࡢࡓࡵẕ࣓࢞ࡣ⦾Ṫᆅ࡛࠶ࡿ◁὾ࢆ┠ᣦࡋ࡚ᩘ༓࢟ࣟࡶ᪑ࢆࡍࡿࡇ࡜ࡶ࠶ࡿࠋࡑࡋ࡚◁὾࡟ࡓ࡝ࡾ╔ࡃ࡜ࠊୖグࡢࡼ࠺࡟ 2 㐌㛫ࡈ࡜࡟⏘༸ࢆ⧞ࡾ㏉ࡍࠋࡇࡢ 2 㐌㛫ࡢ㛫ࡣࠊ䭱ሙ࡟ᡠࡽࡎ࡟⏘༸ࡍࡿ◁὾ࡢ㏆ࡃ࡟࠸ࡿࠋࡇࡢࡓࡵ⏘༸ᆅࡢ㏆ࡃ࡟䭱࡛࠶ࡿᾏⲡࡸᾏ⸴ࡀ࡞࠸࡜ࠊẕ࣓࢞ࡣఱ࠿᭶ࡶ
⤯㣗ࡋ࡚㐣ࡈࡍࡇ࡜࡟࡞ࡿࠋࡑࡋ࡚ࠊࡑࡢᖺࡢ⏘༸ࡀ⤊ࢃࡿ࡜ࠊ෌ࡧᩘ༓࢟ࣟࢆὋ࠸࡛ࠊ
ඖࡢ䭱ሙ࡟ᡠࡿࡢ࡛࠶ࡿࠋ
࢔࣑࣓࢜࢘࢞ࡢᑑ࿨࡟ࡘ࠸࡚ࡣࢃ࠿ࡗ࡚࠸࡞࠸ࠋ࢔࣑࣓࢝࢘࢞ࡣ 60 ᖺ࠿ࡽ 70 ᖺࡄࡽ࠸࡜⪃࠼ࡽࢀ࡚࠸ࡿࠋ࢔࣑࣓࢜࢘࢞ࡣ࢔࣑࣓࢝࢘࢞ࡼࡾࡶᡂ⇍ࢧ࢖ࢬࡀᑡࡋ኱ࡁ࠸ࠋࡇࡢࡓ
ࡵࡶ࠺ᑡࡋ㛗⏕ࡁࡍࡿࡢ࠿ࡶࡋࢀ࡞࠸ࠋ࠸ࡎࢀ࡟ࡋ࡚ࡶࠊᑑ࿨ࢆࡲࡗ࡜࠺࡛ࡁࡿࡶࡢࡣᑡ
࡞ࡃࠊ࡯࡜ࢇ࡝ࡀࢧ࣓࡟くࢃࢀࡓࡾࠊே㛫άືࡢᘢᐖ࡟ࡼࡗ࡚Ṛࢇ࡛ࡋࡲ࠺࡜ᛮࢃࢀࡿࠋ

‫ࢆ࣓࣑࢞࢘ە‬㣗࡭ࡿື≀࢔࣑࣓࢜࢘࢞ࡢ༸ࡸᏊ࣓࢞ࡣࡉࡲࡊࡲ࡞ື≀࡟≺ࢃࢀ࡚࠸ࡿࠋ౛࠼ࡤࠊࢫࢼ࢞ࢽࠊᾏ㫽ࠊ࣊ࣅࠊ࢟ࢶࢿࠊ࣐ࣥࢢ࣮ࢫࠊ࢖ࢱࢳࠊ㔝⏕໬ࡋࡓࣈࢱ࡞࡝ࡀ࠶ࡿࠋ◁὾࡜࠸࠺䭱ࡢஈࡋ࠸⎔ቃࡢ୰࡛ࡣࠊື≀ࡓࡕ࡟࡜ࡗ࡚࣑࣓࢘࢞ࡢ༸ࡣࡲࡓ࡜࡞࠸ࡈ㥅㉮࡛࠶ࢁ࠺ࠋ᪥ᮏ࡛ࡣ௦
⾲ⓗ࡞࣑࣓࢘࢞༸ࡢᤕ㣗⪅࡜ࡋ࡚ࢫࢼ࢞ࢽ㢮ࠊ࢔࣐࢝ࢱࠊࣜࣗ࢘࢟ࣗ࢘࢖ࣀࢩࢩࡀ࠸ࡿࠋ
ࢫࢼ࢞ࢽ㢮ࡣ᪥ᮏ࡛ࡶࡈࡃ
ᬑ㏻࡟⏕ᜥࡋ࡚࠾ࡾࠊࢶࣀ࣓
࢞ࢽ࣭ࢫࢼ࢞ࢽ࣭࣑ࢼ࣑ࢫࢼ
࢞ࢽࡢ 3 ✀㢮ࡀ࠸ࡿࠋ≉࡟ࢶࣀ࣓࢞ࢽ࡜࣑ࢼ࣑ࢫࢼ࢞ࢽࡢ
⏕ᜥᆅࡣࠊ࢔࣑࣓࢜࢘࢞ࡢ⏘༸ᆅ࡜㔜࡞ࡗ࡚࠸࡚ࠊ᪥ᮏࡢ
඲య࡛ࡳࢀࡤ࣑࣓࢘࢞༸࡜Ꮚ
࣓࢞ࡢ᭱኱ࡢᤕ㣗⪅࡛ࡣ࡞࠸ࡔࢁ࠺࠿ࠋᑠ➟ཎㅖᓥ࡛ࡣ඲
⏘༸ᕢࡢ 50㸣௨ୖࡀ㣗ᐖࡉࢀἱἜἱἋἜỾἝỊˊᘙႎễỸἱỾἳҳể‫܇‬Ỿἳỉ਺᫢ᎍᴾ࡚࠸ࡿ࡜࠸࠺ሗ࿌ࡀ࠶ࡿࠋ༡

Ghost crab is one of the main predators of sea turtle eggs andすㅖᓥࡢ◁὾࡛ࡶࠊ࣑࣓࢘࢞

hatchlingsࡢ⏘༸ᕢࡢୖ࡟ࢫࢼ࢞ࢽࡀ᥀
ࡗࡓ✰ࡀࡓࡃࡉࢇ㛤࠸࡚࠸ࡿࡇ࡜ࡀ࠶ࡿࠋࢫࢼ࢞ࢽ㢮ࡣ◁ࢆ᥀ࡗ࡚࣑࣓࢘࢞ࡢ⏘༸ᕢ࡟17ỴỼỸἱỾἳỉʩ‫ރ‬ẇỼἋầἳἋỉɥỆʈẾềẟỦᴾ
Coupling of green turtles. Male green turtle cling to the back of a female when mating.

ᴾ

Sea turtle predators
Eggs and hatchlings of green turtles are predated upon by many animals, such as
Ghost crabs, termites, sea birds, snakes, foxes, mongooses, weasels, and wild boars. Sea
turtle eggs are highly sought after by animals that inhabit beaches, where food sources
are scarce. Major predators in Japan include sand crabs species, the odd-tooth snake,and the Ryukyu boar (Ryukyu is an traditional Japanese term for Okinawa).
Ghost crab species inhabit coastal areas of Japan. Their habitat overlaps with green
turtle rookeries, which may be the reason why they predate the most on sea turtle eggs.
Over 50 % of sea turtle nests are damaged, and many holes dug by ghost crabs are seen
near clutches at Southern Iriomote Island. Ghost crabs feast on eggs by breaking into
nests. They also catch sea turtle hatchlings, which are about the same size as themselves.
Meanwhile, even if ghost crabs dig holes on top of sea turtle clutches, they do notalways reach the eggs. Researchers in the Ogasawara Islands reported that ghost crabs

18౵ධࡋࠊ༸ࢆ㣗࡭ࡿࠋࡲࡓࠊᾏ࡟ྥ࠿࠺㏵୰ࡢᏊ࣓࢞ࢆᤕࡲ࠼࡚ࡋࡲ࠺ࠋࢫࢼ࢞ࢽࡀ⮬㌟
࡜ྠࡌࡄࡽ࠸ࡢ኱ࡁࡉࡢᏊ࣓࢞ࢆᕢ✰࡟ᘬࡁ㎸ࡴࡢ࡛࠶ࡿ࠿ࡽࠊࡑࡢගᬒ࡟ࡣ㦫ࡃࠋࡋ࠿ࡋࠊࢫࢼ࢞ࢽࡣ࣑࣓࢘࢞ࡢ⏘༸ᕢࡢୖ࡟✰ࢆ᥀ࡗ࡚࠸࡚ࡶࠊᚲࡎࡋࡶ༸ࡲ࡛฿㐩ࡋ࡚࠸࡞࠸ࡼ࠺࡛࠶ࡿࠋᑠ➟ཎㅖᓥ࡛ࡢᐇ㦂࡛ࡣࠊேࡀࡓࡔ✰ࢆ᥀ࡗ࡚ࠊࡑࢀࢆᇙࡵᡠࡋࡓሙᡤ࡟
ࡶࠊࢫࢼ࢞ࢽࡢ✰ࡀ㞟୰ࡍࡿ࡜࠸࠺ሗ࿌ࡀ࠶ࡿࠋࡘࡲࡾࠊࢫࢼ࢞ࢽࡣ༢࡟᥀ࡾࡸࡍ࠸࡜ࡇ
ࢁࢆ᥀ࡗ࡚࠸ࡿࡔࡅ࡛ࠊ⏘༸ᕢࢆぢࡘࡅࡿࡢࡣഅ↛࡛࠶ࡿ࡜ゝ࠺ㄝࡶ࠶ࡿࠋᴾ ༡すㅖᓥ࡛ࡢࡳぢࡽࢀࡿ࣑࣓࢘࢞༸ࡢᤕ㣗⪅ࡶ࠸ࡿࠋࡑࢀࡣ࢔࣐࢝ࢱ࡜ࣜࣗ࢘࢟ࣗ࢘࢖
ࣀࢩࢩ࡛࠶ࡿࠋ࢔࣐࢝ࢱࡣ඲㛗ࡀ 1.5m ࡟࡞ࡿ኱ᆺࡢ࣊ࣅ࡛ࠊἈ⦖ᓥࡢࡸࢇࡤࡿᆅᇦࡸ៞Ⰻ
㛫ㅖᓥࡢᒇ჆ẚᓥ࡜ஂሙᓥ࡞࡝࡛࣑࣓࢘࢞༸ࡸᏊ࣓࢞ࡢᤕ㣗ࡀࡳࡽࢀࡿࠋ࢔࣐࢝ࢱࡢᤕ㣗᪉ἲࡣࠊ⏘༸ᕢ࡟┤᥋౵ධࡋ࡚༸ࢆ㣗࡭ࡿࠋ⏘༸ᕢࡢୖ࡛Ꮚ࣓࢞ࡀฟ࡚ࡃࡿࡢࢆᚅࡘࠊ◁὾ࢆᚔᚉࡋ࡚ᙅࡗࡓᏊ࣓࢞ࢆ᥈ࡍ࡞࡝ࡉࡲࡊࡲࣃࢱ࣮ࣥࡀ࠶ࡿࠋ࢔࣐࢝ࢱࡣ࣑࣓࢘࢞⏘༸ᮇ࡟ࡈࡃᬑ㏻࡟༸ࡸᏊ࣓࢞ࢆ㣗࡭࡚࠸ࡿࡀࠊࡇࡢࡼ࠺࡟࣊ࣅࡀ࣓࢝ࢆ㣗࡭ࡿࡢࡣୡ⏺ⓗ࡟
ぢ࡚ࡶࡓ࠸࡬ࢇ⌋ࡋ࠸ࡇ࡜࡛࠶ࡿࠋࣜࣗ࢘࢟ࣗ࢘࢖ࣀࢩࢩࡣ዆⨾ㅖᓥࡼࡾࡶ༡ࡢᓥᕋ࡟⏕ᜥࡋ࡚࠸ࡿࠋ࣑࣓࢘࢞ࡢ༸ࢆ㣗࡭࡚࠸ࡿሙᡤࡣࠊす⾲ᓥࡢ༡ഃࠊ▼ᇉᓥࡢ໭㒊࡜዆⨾ㅖᓥỸἱỾἳỉҳử᫢ỔỦἼἷỸỿἷỸỶἠἉἉᴾ
ᩉ޽Ị཰Ẫ᫲ỉᨂỤủẺ࿢‫ؾ‬ỂẝụẆཎഷễဃസụỉ৆ဦầẝỦᴾ
Ryukyu boars feeding on sea turtle eggs. Islands are scarce in food source. Animals inhabiting in the area
develop surviving skills particular to island life.

19

dig their holes on sites where humans dug, hinting that they choose sites that are easy to
dig and coincidently find sea turtle clutches.
There are also egg hunters specific to the Southern Nansei Islands: the odd-toothsnake and the Ryukyu boar. The odd-tooth snake grows to about 1.5 meters long and is
known to harvest sea turtle eggs in the Yanbaru region of Okinawa, and Yagabi Island
and Kuba Island of theKeramaIslandchain.

They hunt in many ways
such

as

break

clutches,

wait

in

to
until

hatchlings crawl out ofnests,

andsearchforhatchlings worn out fromtrying to reach the sea.
Odd-tooth snake prey on
both eggs and hatchlings
but the case of snake
predation is rare. Ryukyu
boars inhabit the southern
Amami Islands. Sea turtle
eggs are eaten in thesouthern

regionofIriomote Island, north ofIshigaki

Island,andregions in Uge and YoronỴỽἰἑỊẰộằộễ૾ඥỂỸἱỾἳử਺᫢ẴỦẇɥỊҳử੕ẲềჿỆ๼ẾềẟỦẇɦỊᏮЈẲẺ‫܇‬Ỿἳử਺ảềẟỦᴾ
Odd-tooth snakes hunt sea turtles in many ways. Top picture: odd-toothsnake digging in sand in search for eggs. Bottom picture: odd-toothsnake hunting sea turtle hatchling

Islands.

Boars

broad

regions

Europeaninhabitofthecontinent;

however Ryukyu boars are
the

only

nativeboar

species known to eat sea

20ࡢㄳᓥ࣭୚㊰ᓥ࡜୍㒊ࡢᆅᇦ࡟㝈ࡽࢀ࡚࠸ࡿࠋ࢖ࣀࢩࢩࡣ࣮ࣚࣟࢵࣃ኱㝣ࡢᗈ࠸ᆅᇦ࡟⏕ᜥࡋ࡚࠸ࡿࡀࠊᅾ᮶ࡢ࢖ࣀࢩࢩࡀ࣑࣓࢘࢞༸ࢆ㣗࡭ࡿࡇ࡜ࡣࠊࡇࡢࣜࣗ࢘࢟ࣗ࢘࢖ࣀࢩࢩ
ࡋ࠿▱ࡽࢀ࡚࠸࡞࠸ࠋ࢖ࣀࢩࢩࡣ㞧㣗࡛ࡣ࠶ࡿࡀ୺࡟᳜≀㉁ࡢ䭱ࢆ㣗࡭ࡿࡇ࡜ࠊࡑࡋ࡚⮑⑓࡞ᛶ᱁࡞ࡢ࡛◁὾ࡢࡼ࠺࡞㛤ࡅࡓሙᡤࡣ㆙ᡄࡋ࡚ฟ࡚ࡇ࡞࠸ࠊ࡜࠸࠺ࡇ࡜ࡀ⌮⏤࡜ࡋ࡚࠶ࡆࡽࢀࡿࠋࡘࡲࡾᮏ᮶ࠊ࣑࣓࢘࢞༸ࡣ࢖ࣀࢩࢩ࡟࡜ࡗ࡚࠶ࡲࡾ㨩ຊⓗ࡞䭱࡜ࡣゝ࠼࡞࠸ࡢ࡛࠶ࡿࠋ࢔࣐࢝ࢱࡸࣜࣗ࢘࢟ࣗ࢘࢖ࣀࢩࢩࡀ࣑࣓࢘࢞༸ࢆ㣗࡭ࡿࡇ࡜ࡣࠊᓥᕋ࡜࠸࠺㝈ࡽࢀࡓ䭱㈨※ࡢ୰࡛ື≀ࡓࡕࡀ࠶ࡳࡔࡋࡓ⏕ࡁṧࡾࡢᡓ␎࡜࠸࠼ࡿࠋ
ࢧ࣓㢮ࡣࠊ኱ࡁࡃ࡞ࡗࡓ࣑࣓࢘࢞ࡢኳᩛ࡛
࠶ࡾࠊ≉࡟࢖ࢱࢳࢨ࣓ࡀ࣑࣓࢘࢞ࡢᤕ㣗⪅࡜ࡋ࡚᭷ྡ࡛࠶ࡿࠋ࢖ࢱࢳࢨ࣓ࡣయ㛗 4m ௨ୖ࡟࡞ࡿ኱ᆺࡢࢧ࣓࡛ࠊேࢆく࠺ࡇ࡜ࡶ࠶ࡿࠋ
ඵ㔜ᒣ࡛ࡣᖺ࡟ᩘᅇࢧ࣓ࡢ㥑㝖஦ᴗࡀ࠾ࡇ࡞
ࢃࢀ࡚࠸ࡿࡀࠊࡇࡢ࢖ࢱࢳࢨ࣓࠿ࡽ࣑࣓࢘࢞
ࡀฟ࡚ࡃࡿࡇ࡜ࡣከ࠸ࠋࡓ࠸࡚࠸ࡣ࣑࣓࢘࢞
ࡢయࡢ 1 㒊࡛࠶ࡿࡀࠊࡲࡿࡈ࡜ධࡗ࡚࠸ࡿࡇ
࡜ࡶ࠶ࡿࠋඵ㔜ᒣㅖᓥ࡛ࡣ࢔࣑࣓࢜࢘࢞ࡢ 20
㢌࡟ 1 㢌ࡄࡽ࠸ࡢ๭ྜ࡛⫥ࡀ࡞࠿ࡗࡓࡾࠊ⏥ࡽࡀ࠼ࡄࡽࢀࡓࡾࡋ࡚࠸ࡿಶయࡀほᐹࡉࢀࡿࠋ
ࡇࢀࡽࡣ࢖ࢱࢳࢨ࣓࡞࡝ࡢࢧ࣓࡟ࡼࡿညࡳ㊧ࡔ࡜⪃࠼ࡽࢀ࡚࠸ࡿࠋே࠿ࡽぢࢀࡤࠊ࣑࣓࢘࢞ࡀ㣗࡭ࡽࢀࡿࡢࡣ
ྍယࡑ࠺࡞Ẽᣢࡕ࡟࡞ࡿࡀࠊ࣑࣓࢘࢞ࡀከ࠸
࡜ࡇࢁ࡛ࡣࠊࡑࢀࢆ฼⏝ࡍࡿື≀ࡀ࠸ࡿࡇ࡜
ࡣࡈࡃ⮬↛࡞ὶࢀ࡛࠶ࡿࠋ࢖ࣥࢻὒࡢ࣐࣮࢜
࡛ࣥࡣࠊ䭱ࡢஈࡋ࠸஝⇱ᆅᖏ࡟ఫࡴ࢟ࢶࢿࡓ

਺ྒẰủẺỶἑἓἈἳẇᴾࡕࡣ࣑࣓࢘࢞ࡢ༸ࡸᏊ࣓࢞ࢆ㣗࡭ࡿࡇ࡜࡟ࡼ

ỴỼỸἱỾἳử᫢ỔềẟỦẮểờ‫ٶ‬ẟᴾࡗ࡚ࠊࡑࡢᅵᆅ࡛⏕ࡁ࡚࠸ࡅࡿ࡜࠸࠺ሗ࿌ࡶ

ᵲᶇᶅᶃᶐᴾᵱᶆᵿᶐᶉᴾᶒᶆᵿᶒᴾᶕᵿᶑᴾᶁᵿᶓᶅᶆᶒᴾ࠶ࡿࠋぢ᪉ࢆኚ࠼ࡿ࡜ࠊ࣑࣓࢘࢞ࢆ㣗࡭ࡿື

Green turtle found from stomach of tiger shark≀ࡀ࠸ࡿ࡜ࡇࢁࡣࠊࡓࡃࡉࢇࡢ࣑࣓࢘࢞ࡀఫ
ࡴࡇ࡜ࡀ࡛ࡁࡿ⮬↛ࡀ㇏࠿࡞ᆅᇦ࡜ࡶゝ࠼ࡿࠋ

21

turtle eggs. Boars are omnivorous, but feed mainly on plants. They are very cautious so
do not often appear in open areas. Therefore, Ryuku boars feeding on turtle eggs, which
can be found only in open beach area, are rare and specific case of boar species.
Odd-tooth snake and Ryukyu boar predation on sea turtle eggs may be a strategy tosurvive in island environments with limit in food resources.
Sharks are predators of adult sea turtles, and tiger sharks are one of the main predator
species. Tiger sharks grow to over 4 meters long and sometimes attack humans. In the
Yaeyama region, sharks are hunted several times a year for extermination. Sea turtle
parts and even whole sea turtles are sometimes found in the stomachs of tiger sharks. In
addition, one out of twenty green turtles is found without a leg or parts of the carapace,presumably because of tiger shark attacks.
Humans may be against the hunting of sea turtles, but there are many natural
predators of sea turtles. There are reports that fox inhabiting in a dry area of Oman feast
on sea turtle eggs and hatchlings to survive. Habitat of animal species predating on sea
turtles may also be an ideal habitat for sea turtles.

ᙱᘙ޽ỉỸἱỾἳငҳ‫ע‬ẇᝅẦễᐯ໱ầസẾềẟỦᴾẺẪẰỮỉỴỼỸἱỾἳỉငҳầẝụẆộẺҳử᫢ỔỦѣཋẺẼỉ᫢ཋᡲᦋầ঺ụᇌẾềẟỦᴾ
Sea turtle rookery on Iriomote Island. Number of green turtle nest on this beach andthe eggs are hunted by egg-eating animals.

22